Mortgage Amortization Calculator

How This Mortgage Amortization Calculator Works

Every fixed-rate mortgage is amortized the same way: your lender calculates one payment amount that stays constant for the life of the loan, but the mix of interest and principal inside that payment shifts every month. In month one, most of your payment is interest — you're borrowing against the full loan balance, so the interest charge (balance × monthly rate) is at its highest point. As you chip away at the balance, the interest portion shrinks and the principal portion grows, even though the total payment doesn't change. That shifting split is what "amortization" means, and it's why paying extra toward principal early in the loan saves far more interest than the same extra dollar paid in year 25.

This tool runs that exact month-by-month math for you — 360 rows for a 30-year loan, 180 for a 15-year loan — and lets you layer in the variables that actually affect what you pay: private mortgage insurance (PMI) if your down payment is under 20%, property taxes and homeowners insurance if you escrow them into your payment, HOA dues, and any extra principal payments you plan to make. Toggle biweekly payments to see how simply splitting your payment in half every two weeks (26 half-payments = 13 full payments a year) accelerates payoff without changing your budget much.

Worked Example: $400,000 Home, 20% Down, 6.5%, 30 Years

Say you're buying a $400,000 home with 20% down ($80,000), leaving a $320,000 loan at 6.5% over 30 years. Your principal-and-interest payment comes out to roughly $2,022/month. Over the full 30 years you'll pay about $407,900 in interest — more than the original loan amount — on top of repaying the $320,000 principal, for a total of just over $727,900 paid to borrow $320,000.

Now add just $200/month in extra principal payments from day one. The loan payoff moves up by roughly 5.5 years, and total interest drops by around $70,000. That's the entire point of running your numbers through an amortization calculator instead of just looking at the monthly payment quoted by a lender: the monthly number tells you what you can afford today, but the schedule tells you what the loan actually costs over its life — and how much control you have over that cost.

Ways to Pay Off Your Mortgage Faster

Every one of these strategies works by increasing the principal portion of what you pay, which is the only lever you have once your rate and term are locked in:

• Extra monthly payments — even a modest, consistent amount compounds significantly over a 30-year term. Model your own numbers on our extra payments calculator.
• Biweekly payments — splitting your payment in two every two weeks results in one extra full payment per year, almost painlessly.
• A lump-sum recast— if you come into money (bonus, inheritance, home sale proceeds) and don't want to refinance, a mortgage recast re-amortizes your existing balance into a lower payment at your current rate.
• Refinancing — if rates have dropped meaningfully since you took out your loan, run the numbers on our refinance calculator to see your real break-even point after closing costs.
• Dropping PMI early — once your loan-to-value ratio hits 80%, you can usually request PMI removal rather than waiting for automatic cancellation. See how extra payments accelerate that date on our PITI calculator.

What Determines Your Interest Rate

The rate you enter above is the single biggest lever in this whole calculation — a 1-point difference on a $400,000, 30-year loan changes your monthly payment by roughly $250 and your lifetime interest by tens of thousands of dollars. Lenders price your rate off a handful of factors you can influence before you ever apply:

• Credit score. The spread between a 620 borrower and a 760+ borrower is routinely 0.5-1 full percentage point on a conventional loan. Pulling your score up even one tier before you shop can be worth more than negotiating with a single lender.
• Down payment / loan-to-value (LTV).Putting down 20% instead of 5% not only removes PMI (see below) but often earns a modestly better rate, since the lender's exposure if you default is lower.
• Debt-to-income (DTI) ratio. Lenders compare your total monthly debt payments (including the new mortgage) to your gross income. Staying comfortably under the common 43% DTI ceiling — ideally under 36% — widens your rate options.
• Loan term and type.A 15-year term typically prices 0.5-0.75 points below a 30-year term on the same day, because the lender's money is at risk for half as long. FHA, VA, and USDA loans carry their own rate and mortgage-insurance rules that can price better or worse than a conventional loan depending on your situation.
• Points and lender credits.You can pay upfront "discount points" to buy your rate down, or take a slightly higher rate in exchange for a lender credit toward closing costs — run both scenarios through this calculator with different rate/loan-amount combinations before deciding which trade is worth it for how long you plan to keep the loan.

None of these factors are inputs this calculator can look up for you — they come from your actual application — but changing the rate field above to test a best-case and worst-case scenario before you apply is exactly how to use this tool to negotiate from an informed position.

Reading Your Amortization Schedule

The table above groups your loan by year, with a "Show months" toggle to expand any year into its individual monthly rows. Each row breaks your payment into the same five pieces every lender's schedule uses:

• Principal paid — how much of that year's payments reduced your loan balance.
• Interest paid — the cost of borrowing for that year, calculated on whatever balance remained at the start of each month.
• Extra payment — any additional amount you added beyond the required payment, which comes entirely off principal.
• PMI — private mortgage insurance, shown only while your loan-to-value ratio sits above the cancellation threshold.
• Ending balance — what you'd still owe if you sold or refinanced at the end of that year.

Watch the crossover point where the principal column overtakes the interest column — on a typical 30-year loan at today's rates, that happens somewhere between year 15 and year 20. Everything paid before that crossover is weighted much more heavily toward interest than most borrowers expect, which is exactly why extra payments made in the first five to ten years do so much more work than the same dollar amount paid later.

How We Calculate These Numbers

Every figure on this page comes from the standard fixed-rate amortization formula: M = P × [r(1+r)ⁿ] / [(1+r)ⁿ − 1], where P is your loan principal, r is your interest rate divided by 12, and n is your total number of monthly payments. We generate a full month-by-month schedule from that formula rather than approximating, so the numbers you see here match what you'd get from a closing disclosure or lender-provided amortization table for the same inputs. For background on how rates and PMI rules work more broadly, see Freddie Mac's Primary Mortgage Market Survey and the CFPB's guidance on PMI cancellation. For a full breakdown of the formula and every variable this calculator supports, see our calculation methodology page.